Cs adsorption on Si(001) surface: ab initio study

First-principles calculations using density functional theory based on norm-conserving pseudopotentials have been performed to investigate the Cs adsorption on the Si(001) surface for 0.5 and 1 ML coverages. We found that the saturation coverage corresponds to 1 ML adsorption with two Cs atoms occupying the double layer model sites. While the 0.5 ML covered surface is of metallic nature, we found that 1 ML of Cs adsorption corresponds to saturation coverage and leads to a semiconducting surface. The results for the electronic behavior and surface work function suggest that adsorption of Cs takes place via polarized covalent bonding.Comment: 8 pages, 7 figure

Growth of (110) Diamond using pure Dicarbon

We use a density-functional based tight-binding method to study diamond growth steps by depositing dicarbon species onto a hydrogen-free diamond (110) surface. Subsequent C_2 molecules are deposited on an initially clean surface, in the vicinity of a growing adsorbate cluster, and finally, near vacancies just before completion of a full new monolayer. The preferred growth stages arise from C_2n clusters in near ideal lattice positions forming zigzag chains running along the [-110] direction parallel to the surface. The adsorption energies are consistently exothermic by 8--10 eV per C_2, depending on the size of the cluster. The deposition barriers for these processes are in the range of 0.0--0.6 eV. For deposition sites above C_2n clusters the adsorption energies are smaller by 3 eV, but diffusion to more stable positions is feasible. We also perform simulations of the diffusion of C_2 molecules on the surface in the vicinity of existing adsorbate clusters using an augmented Lagrangian penalty method. We find migration barriers in excess of 3 eV on the clean surface, and 0.6--1.0 eV on top of graphene-like adsorbates. The barrier heights and pathways indicate that the growth from gaseous dicarbons proceeds either by direct adsorption onto clean sites or after migration on top of the existing C_2n chains.Comment: 8 Pages, 7 figure

Deslizamientos naturales y comunidades pionera de ecosistemas montanos al occidente del parque nacional podocarpus (ecuador)

El Parque Nacional Podocarpus (PNP), ubicado al sur del Ecuador, ocupa una posición climatológica clave con respecto a la deflexión de Huancabamba aledaña a esta área hacia el sur, que ocasiona una barrera natural de distribución de especies y por otro lado este aislamiento biogeográfíco ha originado especiación florística en algunas especies. La geografía accidentada de esta región, sumada a la escasa capa vegetal y precipitaciones que superan los 6000 mm en los páramos, ocasiona impactos severos en los flancos orientales y occidentales de la baja Cordillera Oriental que no sobrepasa los 3700 m, en sus límites altitudinales más altos. Es aquí donde existe una dinámica alta de deslizamientos, los mismos que si bien afectan la diversidad vegetal, también son considerados un motor generador de continuos procesos de regeneración. Se establecieron 138 parcelas, distribuidas a o largo de un gradiente latitudinal y altitudinal, de 1 x 5m al occidente del PNP, encontrándose 218 especies representantes de 180 géneros y 51 familias; el piso altitudinal de mayor diversidad está a los 2700 m. El análisis TWINSPAN separó nueve comunidades vegetales, mientras que el análisis multivariado CANOCO, determinó que las características edafológicas influyen en la composición de la vegetación, mientras que la altitud y la pendiente no establecen notable diferencia

Coronary-Artery Bypass Surgery in Patients with Ischemic Cardiomyopathy

BACKGROUND: The survival benefit of a strategy of coronary-artery bypass grafting (CABG) added to guideline-directed medical therapy, as compared with medical therapy alone, in patients with coronary artery disease, heart failure, and severe left ventricular systolic dysfunction remains unclear. METHODS: From July 2002 to May 2007, a total of 1212 patients with an ejection fraction of 35% or less and coronary artery disease amenable to CABG were randomly assigned to undergo CABG plus medical therapy (CABG group, 610 patients) or medical therapy alone (medical-therapy group, 602 patients). The primary outcome was death from any cause. Major secondary outcomes included death from cardiovascular causes and death from any cause or hospitalization for cardiovascular causes. The median duration of follow-up, including the current extended-follow-up study, was 9.8 years. RESULTS: A primary outcome event occurred in 359 patients (58.9%) in the CABG group and in 398 patients (66.1%) in the medical-therapy group (hazard ratio with CABG vs. medical therapy, 0.84; 95% confidence interval [CI], 0.73 to 0.97; P=0.02 by log-rank test). A total of 247 patients (40.5%) in the CABG group and 297 patients (49.3%) in the medical-therapy group died from cardiovascular causes (hazard ratio, 0.79; 95% CI, 0.66 to 0.93; P=0.006 by log-rank test). Death from any cause or hospitalization for cardiovascular causes occurred in 467 patients (76.6%) in the CABG group and in 524 patients (87.0%) in the medical-therapy group (hazard ratio, 0.72; 95% CI, 0.64 to 0.82; P<0.001 by log-rank test). CONCLUSIONS: In a cohort of patients with ischemic cardiomyopathy, the rates of death from any cause, death from cardiovascular causes, and death from any cause or hospitalization for cardiovascular causes were significantly lower over 10 years among patients who underwent CABG in addition to receiving medical therapy than among those who received medical therapy alone. (Funded by the National Institutes of Health; STICH [and STICHES] ClinicalTrials.gov number, NCT00023595.)

A Direct Fluorescent Activity Assay for Glycosyltransferases Enables Convenient High‐Throughput Screening : Application to O‐GlcNAc Transferase

Glycosyltransferases carry out important cellular functions in species ranging from bacteria to humans. Despite their essential roles in biology, simple and robust activity assays that can be easily applied to high-throughput screening for inhibitors of these enzymes have been challenging to develop. Herein, we report a bead-based strategy to measure the group-transfer activity of glycosyltransferases sensitively using simple fluorescence measurements, without the need for coupled enzymes or secondary reactions. We validate the performance and accuracy of the assay using O-GlcNAc transferase (OGT) as a model system through detailed Michaelis–Menten kinetic analysis of various substrates and inhibitors. Optimization of this assay and application to high-throughput screening enabled screening for inhibitors of OGT, leading to a novel inhibitory scaffold. We believe this assay will prove valuable not only for the study of OGT, but also more widely as a general approach for the screening of glycosyltransferases and other group-transfer enzymes

DESLIZAMIENTOS NATURALES Y COMUNIDADES PIONERA DE ECOSISTEMAS MONTANOS AL OCCIDENTE DEL PARQUE NACIONAL PODOCARPUS (ECUADOR)

El Parque Nacional Podocarpus (PNP), ubicado al sur del Ecuador, ocupa una&nbsp;posici&oacute;n climatol&oacute;gica clave con respecto a la deflexi&oacute;n de Huancabamba aleda&ntilde;a&nbsp;a esta &aacute;rea hacia el sur, que ocasiona una barrera natural de distribuci&oacute;n de especies&nbsp;y por otro lado este aislamiento biogeogr&aacute;f&iacute;co ha originado especiaci&oacute;n flor&iacute;stica en&nbsp;algunas especies. La geograf&iacute;a accidentada de esta regi&oacute;n, sumada a la escasa capa&nbsp;vegetal y precipitaciones que superan los 6000 mm en los p&aacute;ramos, ocasiona impactos&nbsp;severos en los flancos orientales y occidentales de la baja Cordillera Oriental que no&nbsp;sobrepasa los 3700 m, en sus l&iacute;mites altitudinales m&aacute;s altos. Es aqu&iacute; donde existe&nbsp;una din&aacute;mica alta de deslizamientos, los mismos que si bien afectan la diversidad&nbsp;vegetal, tambi&eacute;n son considerados un motor generador de continuos procesos de&nbsp;regeneraci&oacute;n. Se establecieron 138 parcelas, distribuidas a o largo de un gradiente&nbsp;latitudinal y altitudinal, de 1 x 5m al occidente del PNP, encontr&aacute;ndose 218 especies&nbsp;representantes de 180 g&eacute;neros y 51 familias; el piso altitudinal de mayor diversidad&nbsp;est&aacute; a los 2700 m. El an&aacute;lisis TWINSPAN separ&oacute; nueve comunidades vegetales,&nbsp;mientras que el an&aacute;lisis multivariado CANOCO, determin&oacute; que las caracter&iacute;sticas&nbsp;edafol&oacute;gicas influyen en la composici&oacute;n de la vegetaci&oacute;n, mientras que la altitud y&nbsp;la pendiente no establecen notable diferencia.</div

DESLIZAMIENTOS NATURALES Y COMUNIDADES PIONERA DE ECOSISTEMAS MONTANOS AL OCCIDENTE DEL PARQUE NACIONAL PODOCARPUS (ECUADOR)

El Parque Nacional Podocarpus (PNP), ubicado al sur del Ecuador, ocupa una&nbsp;posici&oacute;n climatol&oacute;gica clave con respecto a la deflexi&oacute;n de Huancabamba aleda&ntilde;a&nbsp;a esta &aacute;rea hacia el sur, que ocasiona una barrera natural de distribuci&oacute;n de especies&nbsp;y por otro lado este aislamiento biogeogr&aacute;f&iacute;co ha originado especiaci&oacute;n flor&iacute;stica en&nbsp;algunas especies. La geograf&iacute;a accidentada de esta regi&oacute;n, sumada a la escasa capa&nbsp;vegetal y precipitaciones que superan los 6000 mm en los p&aacute;ramos, ocasiona impactos&nbsp;severos en los flancos orientales y occidentales de la baja Cordillera Oriental que no&nbsp;sobrepasa los 3700 m, en sus l&iacute;mites altitudinales m&aacute;s altos. Es aqu&iacute; donde existe&nbsp;una din&aacute;mica alta de deslizamientos, los mismos que si bien afectan la diversidad&nbsp;vegetal, tambi&eacute;n son considerados un motor generador de continuos procesos de&nbsp;regeneraci&oacute;n. Se establecieron 138 parcelas, distribuidas a o largo de un gradiente&nbsp;latitudinal y altitudinal, de 1 x 5m al occidente del PNP, encontr&aacute;ndose 218 especies&nbsp;representantes de 180 g&eacute;neros y 51 familias; el piso altitudinal de mayor diversidad&nbsp;est&aacute; a los 2700 m. El an&aacute;lisis TWINSPAN separ&oacute; nueve comunidades vegetales,&nbsp;mientras que el an&aacute;lisis multivariado CANOCO, determin&oacute; que las caracter&iacute;sticas&nbsp;edafol&oacute;gicas influyen en la composici&oacute;n de la vegetaci&oacute;n, mientras que la altitud y&nbsp;la pendiente no establecen notable diferencia